Light emitting diodes (LEDs) have been widespread used for lighting with great brightness. Typically, an LED includes a multilayered structure having a p-type semiconductor, an n-type semiconductor and an active layer sandwiched between the p- and n-type semiconductors, p- and n-electrodes placed on the surfaces of the multilayered structure. In operation, a current is injected into the LED from the p- and n-electrodes, which spreads into the respective semiconductor layers. Light is generated when the current flows across the active layer because of the recombination of minority carriers at the active layer. Generally, the generated light from the active layer may be reflected to different degrees, thereby degrading the light extraction efficiency.
In order to improve the light extraction efficiency, microstructures formed on a surface where the light exits outside are usually employed to reduce the light reflection. However, the microstructures are usually formed by photolithography and/or etching, which inevitably increases the complexity and cost of manufacturing. On the other hand, when the generated light from the active layer is transmitted to the metal p- and/or n-electrodes, most of the transmitted light may be absorbed therein, which reduces the light emission efficiency.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.